The present invention relates to an apparatus which enables a coordinate positioning machine (such as a machine tool) to determine the position of an object relative to a reference point. It may, for example, be employed on a machine tool for toolsetting operations.
A known tool setting device for use on a machine tool includes a light source which generates a fine beam of light which is incident upon a detector. During a toolsetting operation, the machine is operated to move the tool in a direction transverse to the direction of propagation of the light beam until a part of the tool interrupts passage of the light beam. Detection of this interruption results in the generation of a trigger signal in the detecting unit, which is used by the machine to establish the relative position of its moving parts in order to determine dimensions of the tool. Such devices are known, for example, from German Patent Nos. DE 42 385 04 and DE 42 448 69, French Patent No. 2,343,555, European Patent No. 98,930 and U.S. Pat. No. 4,518,257.
The devices disclosed in the above-mentioned patent specifications use a narrow light beam into or through which the tool is passed. The detection units detect when the tool breaks into the beam from the resulting drop in the intensity of the light falling on them.
The devices may be used additionally for measuring the length or diameter of a tool to monitor tool breakage or wear.
This additional functionality is produced by providing a plurality of outputs from the device which are individually connected to the input ports of the machine controller.
A problem arises however, with some controllers which have insufficient input ports for receiving all of the outputs. This has hitherto prevented the retrofitting of such multi-function devices to such controllers without losing much of the functionality.
An object of the present invention is to overcome this problem and to provide a device which is retrofittable to a controller with less input ports than there are outputs from the device, even a controller with only one input port, while preserving all of the functionality of the device.
According to the present invention there is provided a measuring system for a machine tool having a controller, wherein the measuring system includes a programmable device which produces a plurality of different output signals, and the controller has less input ports for receiving output signals from the programmable device than the number of output signals produced by the programmable device, and further wherein the controller is programmed to produce a plurality of signals to be sent selectively to the programmable device of the measuring system as input signals, said programmable device being responsive to the receipt of a particular input signal to connect a corresponding one of the output signals to the input of the controller.